Chuck particularly for machining marble and the like

Abstract: The present invention relates to a chuck (1) particularly usable in the machining of marble and the like. The chuck (1) comprises a variable-speed motor (3) provided with a first fixed shaft (7) which interacts with a second flexible transmission shaft (10). The flexible shaft (10) in turn interacts with means (12) that are suitable to transmit motion to a third floating shaft (11) provided with an abrasive or diamondized element (23). Means (19) are arranged radially to the third floating shaft (11) to reposition it along the same axis as the first shaft (7). A chuck is thus obtained that allows to keep the abrasive material constantly in contact with the material to be machined, eliminating any clearance due to the wear of the abrasive material itself.

Description: The present invention relates to a chuck which is used in various fields and particularly in the machining of marble and the like to shape and/or polish the edges of slabs in the most disparate shapes. Machines suitable to shape or polish slabs of stony material are currently known which are essentially constituted by a machining surface on which the slab is kept motionless and is shaped by a movable chuck assembly that produces the intended geometrical shapes. The mills of the chuck assembly can thus be mounted on a support which is rotatable with respect to suitable gears which are laterally rigidly coupled to the frame of the machine so as to allow to obtain, for example, a torus-like profile. In these known machines, in which machining thus occurs essentially in a straight line, there is a large number of mills arranged sequentially with respect to one another. The slab of stony material is therefore initially machined and then polished: this last process, however, cannot always be achieved in an optimum manner since, due to the wear of the abrasive grinding wheels, after some time said grinding wheels no longer polish the slab uniformly. The user is therefore periodically forced to manually polish the slabs and therefore to perform a finishing operation which can no longer be achieved by the machine. As a partial solution to this drawback, it is known to manufacture machines wherein the tools that support the abrasive grinding wheels are subjected to discrete movements according to preset machining times; even this solution, however, is not optimum, since optimum polishing is not always achieved due to the fact that each slab of stony material has a specific and well-defined hardness. All this either produces a clearance between the abrasive grinding wheel and the slab of stony material after a given time, or causes excessive abrasion due to the fact that the discrete movement applied to the grinding wheel has not taken into account the greater hardness of the material. FR-A-2 370 553 discloses a chuck for grinding and polishing comprising a motor driven first shaft which is connected to a second flexible transmission shaft which interacts with a connecting flange to convey the rotative motion of the motor to a tool carrying pin. The tool carrying pin is provided with an abrasive element. Moreover, a compression spring is provided to vertically reposition the tool carrying pin along the axis of the first shaft. The tool carrying pin does however not mantain always the same orientation to the workpiece, because its axis can be inclined with respect to the axis of the first shaft. The principal aim of the present invention is therefore to eliminate the drawbacks described above in known types, by providing a chuck that allows to achieve optimum polishing of slabs of stony material and thus of marbles and the like independently of the degree of wear of the grinding wheels and of the hardness of said slabs. Within the scope of this aim, an important object is to provide a chuck wherein optimum polishing is achieved by using a structure that is simple and can be obtained with known machines and equipment. Another object is to provide a chuck that is reliable and safe in use and has low manufacturing costs. This aim, these objects and others which will become apparent hereinafter are achieved by a chuck particularly for machining marble and the like as defined in the appended claims. Further characteristics and advantages of the invention will become apparent from the following detailed description of a particular but not exclusive embodiment thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a sectional view of the chuck; figure 2 is a sectional view, taken along the plane II-II of figure 1; figure 3 is a view, similar to the preceding one, of the condition in which the third floating shaft is axially offset with respect to the first shaft of the motor. With reference to the above figures, the reference numeral 1 designates the chuck, particularly usable for machining stony products 2 such as marble or the like, which comprises a variable-speed motor 3 which transmits motion to a first fixed shaft 7 by means of a first driving pulley 4 and a second driven pulley 5 which are mutually connected by an appropriately provided belt 6. Said first fixed shaft interacts with appropriately provided first bearings 8a and 8b which are arranged inside a suitable body 9. The end of a second flexible transmission shaft 10 is keyed to the free ends of the first shaft 7; the other end of said second shaft interacts with means which are suitable to transmit motion to a third floating shaft 11. Said means are constituted by a grooved secondary shaft 12 which is present at one end of the second flexible transmission shaft 10 and slides axially with respect to a complementarily shaped bush 13. Said third floating shaft 11 can naturally rotate with respect to its own axis and can also move radially in all directions by virtue of the presence of suitable means, such as a floating central support 14 which is shaped like an annulus; a flange 15 is associated in an upward region with said support and supports a first sliding block 16, whereas a second sliding block 17 is associated with said support in a downward region. Said first flange 15 and said second sliding block 17 are accommodated within the body 9 which is closed in a downward region by a suitable self-centering locking ring 18. The central floating support 14, together with the flange 15 and with the first and second sliding blocks, is constantly in contact with a plurality of pistons 19 which are arranged radially with respect to the third floating shaft 11; said pistons push by means of suitable second bearings 20. Each one of said pistons 19 is connected to a suitable piston body 21, which is interposed between the first sliding block 16 and the second sliding block 17, which act as a guide for the radial movement of said pistons. Said piston body 21 comprises an air reservoir 22 having a circular shape and from which the pistons protrude radially. The air inside the reservoir can thus have a pressure that is adjustable according to the requirements. In fact, by varying the internal pressure of the reservoir the thrust of the pistons 19 decreases or increases, producing a consequently greater thrust at the abrasive material 23 which is connected to a mill 24 which is rigidly coupled to the free end of the third floating shaft 14 which protrudes outside the ring 18. Said self-centering locking ring acts at the second sliding block 17: by tightening it, said ring locks the translatory motion of said second sliding block and thus also locks the movement of the third floating shaft 11. This solution allows to use the chuck by locking for example the axis of the third floating shaft 11 at the axis of the first fixed shaft 7, so as to use the chuck like a usual and known edge shaping chuck. The innovative operation of the chuck instead resides in that the third floating shaft 11 is made to work at the edge of the stony material 2 so that it is axially offset with respect to the axis of the first fixed shaft 7: in this manner a constant thrust of the abrasive material 23 on the material is achieved, since the pistons 19 tend to axially align the third floating shaft 11 with the first fixed shaft 7. By varying the pressure inside the reservoir 22 a greater or smaller thrust of the pistons and thus a greater or smaller thrust of the abrasive material towards the material to be machined is in fact achieved. It has thus been observed that the invention has achieved the intended aim and objects, a chuck having been provided which allows to polish the edges of stony materials such as marble and the like in an optimum manner, since continuous contact of the abrasive material on the edge of the material is ensured, thus eliminating any clearance due to the wear of said abrasive material. Polishing is optimum even if it is necessary to machine stony materials that have different degrees of hardness, since the thrust of the pistons on the third floating shaft is optimum and therefore the abrasive material is constantly kept in contact with the material to be polished. Advantageously, there is a suitable fluid-actuated joint 25 which allows to introduce water in an appropriately provided channel 26 arranged inside the third floating shaft 11 and connected to the underlying mill 24 and, by means of suitable ducts 27, to the outer lateral surface of the abrasive material 23, so as to allow to cool the surface of said abrasive material that works in contact with the stony material 2. The invention is naturally susceptible to numerous modifications and variations, all of which are within the scope of the same inventive concept. The materials and the dimensions which constitute the individual components of the chuck may also naturally be the most pertinent according to the specific requirements. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: Chuck particularly for machining marble and the like comprising a motor (3) provided with a first fixed shaft (7) which is connected to a second flexible transmission shaft (10) which interacts with means (12) that are suitable to transmit motion to a third floating shaft (11) provided with an abrasive or a diamondized element (23), means (19) being arranged radially with respect to said third floating shaft (11) to reposition said third floating shaft (11) along the same axis as said first fixed shaft (7), said third floating shaft (11) being both rotatable to its own axis and movable radially with respect thereto. Chuck according to claim 1, characterized in that said motor (3) is a variable-speed motor, said motor (3) transmitting motion to said first fixed shaft (7) by means of a first driving pulley (4) and of a second driven pulley (5) which are mutually connected by a belt (6), said first fixed shaft (7) interacting with first bearings (8a, 8b) contained within a suitable body (9). Chuck according to claims 1 or 2, characterized in that the end of said second flexible transmission shaft (10) is keyed at the free end of said first fixed shaft (7) and is shaped, at its other end, so as to form a grooved secondary shaft (12) which is axially slideable with respect to a complementarily grooved bush (13). Chuck according to claim 3, characterized in that said bush (13) is rigidly coupled to said third floating shaft (11). Chuck according to one or more of the preceding claims, characterized in that it comprises: a floating central support (14) which is shaped like an annulus; a flange (15) which is coupled to said floating central support (14) at an upward region of said floating central support (14) facing said second flexible transmission shaft (10), said flange (15) supporting a first sliding block (16); and a second sliding block (17) which is coupled to said floating central support (14) in a downward region of said floating central support (14) facing said third floating shaft (11), said first and second sliding blocks (16, 17) supporting said means (19) to reposition said third floating shaft (11). Chuck according to claim 5, characterized in that said first flange (15) and said first and second sliding blocks (16, 17) are accommodated within said suitable body (9), said suitable body (9) being coupled to a self-centering locking ring (18) in a downward region of said suitable body (9), said selfcentering locking ring (18) closing said suitable body (9) at said downward region thereof, said self-centering locking ring (18) acting on said second sliding block (17), the tightening of said self-centering locking ring (18) locking the translatory motion of said second sliding block (17). Chuck according to claims 5 or 6, characterized in that said means (19) to reposition said third floating shaft (11) comprises a plurality of pistons (19) which is associated radially and slidingly with said floating central support (14), said pistons (19) being suitable to push, and pull said central floating support (14) and thus said third floating shaft (11) by virtue of suitable second bearings (20). Chuck according to claim 7, characterized in that each one of said pistons (19) is slidingly and sealingly associated, at one end, with a piston body (21) which is interposed between said first and said second sliding blocks (16, 17), each said piston body (21) acting as a guide for the movement of a respective one of said pistons (19) radially with respect to said third floating shaft (11). Chuck according to claim 8, characterized in that each said piston body (21) is circular and connects to an annular air reservoir (22) from which said pistons (19) protrude radially. Chuck according to claim 9, characterized in that said annular air reservoir (22) is connected to at least one delivery and to at least one intake to determine the pressure inside it. Chuck according to one or more of the preceding claims, characterized in that said third floating shaft (11) has one end which protrudes outside said self-centering locking ring (18) and with which a tool, such as for example a mill (24), is associated, said abrasive or diamondized element (23) being associated with said mill (24) for machining the edge of a stony material (2). Chuck according to one or more of the preceding claims, characterized in that it comprises a fluid-actuated joint (25) for introducing water inside a channel (26) which is formed in said third floating shaft (11) and is connected to said underlying tool (24) and, by means of suitable ducts (27), to the outer lateral surface of said abrasive or diamondized material (23). Chuck according to one or more of the preceding claims, characterized in that said means (19) to reposition said third floating shaft (11) are adapted to radially move in all directions said third floating shaft (11) in respect to its own axis.

Inventors: PEGORARO ERMENEGILDO, PEGORARO, ERMENEGILDO
Applicants: PE MAC SPA FA, FA.PE.MAC.SPA
Application year: 1994
Main classification: B24B41
IPC codes: B23Q1, B24B41